101955 Bennu (provisional designation 1999 RQ₃₆) is a carbonaceous asteroid in the Apollo group that was discovered by the LINEAR Project on September 11, 1999. It is a potential Earth impactor that is listed on the Sentry Risk Table with the second-highest rating on the Palermo Technical Impact Hazard Scale, due to a 1-in-2,700 chance of impacting Earth in the late 22nd century. It is the planned target of the OSIRIS-REx mission which is intended to return samples to Earth in 2023 for further study.

101955 Bennu has a mean diameter of approximately 492 m (1,614 ft; 0.306 mi) and has been observed extensively with the Arecibo Observatory Planetary Radar and the Goldstone Deep Space Network.

Asteroid Bennu has a roughly spheroidal shape, which resembles a spinning top. The direction of rotation about its axis is retrograde with respect to its orbit. Bennu has a fairly smooth shape with one prominent 7001100000000000000♠10–20 m boulder on its surface, in the southern hemisphere.

There is a well-defined ridge along the equator of asteroid Bennu. This presence of this ridge suggests that fine-grained regolith particles have accumulated in this area, possibly due to its low gravity and fast rotation.

Observations of this minor planet by the Spitzer Space Telescope in 2007 gave an effective diameter of 7002484000000000000♠484±10 m, which is in line with other studies. It has a low visible geometric albedo of 6998460000000000000♠0.046±0.005. The thermal inertia was measured and found to vary by ±19% during each rotational period. The data suggest that the regolith grain size is moderate, ranging from several millimeters up to a centimeter, and evenly distributed longitudinally. No emission from a potential dust coma has been detected around asteroid Bennu, which puts a limit of 10⁶ g of dust within a radius of 4750 km.

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